linux-kernel - Re: [PATCH 1/5] mm: vmscan: Do not writeback filesystem pages in direct reclaim

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Thu, 14 Jul 2011 00:46:43 -0400
From:	Christoph Hellwig <hch@...radead.org>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	Mel Gorman <mgorman@...e.de>, Linux-MM <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>, XFS <xfs@....sgi.com>,
	Dave Chinner <david@...morbit.com>,
	Christoph Hellwig <hch@...radead.org>,
	Johannes Weiner <jweiner@...hat.com>,
	Wu Fengguang <fengguang.wu@...el.com>, Jan Kara <jack@...e.cz>,
	Rik van Riel <riel@...hat.com>,
	Minchan Kim <minchan.kim@...il.com>
Subject: Re: [PATCH 1/5] mm: vmscan: Do not writeback filesystem pages in
 direct reclaim

On Thu, Jul 14, 2011 at 10:38:01AM +0900, KAMEZAWA Hiroyuki wrote:
> > +			/*
> > +			 * Only kswapd can writeback filesystem pages to
> > +			 * avoid risk of stack overflow
> > +			 */
> > +			if (page_is_file_cache(page) && !current_is_kswapd()) {
> > +				inc_zone_page_state(page, NR_VMSCAN_WRITE_SKIP);
> > +				goto keep_locked;
> > +			}
> > +
> 
> 
> This will cause tons of memcg OOM kill because we have no help of kswapd (now).

XFS and btrfs already disable writeback from memcg context, as does ext4
for the typical non-overwrite workloads, and none has fallen apart.

In fact there's no way we can enable them as the memcg calling contexts
tend to have massive stack usage.

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/